This invention is concerned with an improved process for the preparation of 2,6-dialkylaniline which comprises the reaction of a 1-nitroalkene with a 1,3-alkadiene to form a dialkylnitrocyclohexene adduct and subsequent reaction of the resulting adduct with hydrogen in the presence of a hydrogenation catalyst to form the corresponding dialkylcyclohexyl amine, followed by dehydrogenation with aqueous ammonia in the presence of a dehydrogenation catalyst.
One method of preparing 2,6-dialkylaniline is by the amination of hydroxyaromatics. U.S. Pat. No. 3,931,298 describes a process for the preparation of aromatic amines by the reaction of hydroxy-substituted aromatic compounds with ammonia in the presence of a catalytic amount of a cyclohexanone and in contact with a hydrogen transfer catalyst.
U.S. Pat. No. 3,960,962 describes a related process wherein aromatic hydroxy compounds are converted to the corresponding aromatic amine by reaction with ammonia in the presence of a cyclohexanone promoter and a catalyst comprising metallic palladium bonded to a phosphinated polystyrene resin.
In U.S. Pat. No. 3,965,182 aromatic amines are made by reacting a phenol with aluminum nitride and either ammonia or a primary or secondary amine.
U.S. Pat. No. 3,801,642 is concerned with a process for replacing an aromatic hydroxyl group with an amine group by forming a metal aryloxide from the corresponding aromatic hydroxy compound and reacting the metal aryloxide with ammonia or a primary or secondary amine in the presence of a Friedel-Crafts catalyst.
U.S. Pat. No. 4,125,560 describes the direct amination of phenols with amines by the ammonolysis of phenols in a liquid phase under pressure with an aqueous ammonia solution containing a catalytic amount of an ammonium salt.
U.S. Pat. No. 3,219,704 describes the preparation of aromatic amines by the condensation of six-membered alicyclic ketones and ammonia compounds with a dehydrogenation catalyst, wherein the molar portion of the ketone is at least substantially equal to the ammonia compound.
In U.S. Pat. No. 3,442,950 aminated benzenes are prepared by catalytically reacting a cyclohexanol with an aminating agent. When cyclohexanone is present in the cyclohexanol component, the reaction is initiated in the presence of one mole of hydrogen per mole of cyclohexanone.
An article by E. G. Kataev and P. S. Matveeva in the Journal of General Chemistry, U.S.S.R., volume 23, pages 413-417 (1953) describes the reaction of piperylene with nitroamylene to form 2-methyl-6-n-propyl-1-nitrocyclohex-3-ene, but does not teach the preparation of the corresponding aromatic amine.
Dialkylanilines, and in particular 2,6-dialkylanilines, are useful intermediates for a variety of compounds having herbicidal and fungicidal activity.